Caspase-mediated cleavage of focal adhesion kinase pp125FAK and disassembly of focal adhesions in human endothelial cell apoptosis.
Normal endothelial and epithelial cells undergo apoptosis when cell adhesion and spreading are prevented, implying a requirement for antiapoptotic signals from the extracellular matrix for cell survival. We investigated some of the molecular changes occurring in focal adhesions during growth factor deprivation-induced apoptosis in confluent monolayers of human umbilical vein endothelial cells. Among the first morphologic changes after initiation of the apoptotic process are membrane blebbing, loss of focal adhesion sites, and retraction from the matrix followed by detachment. We observe a specific proteolytic cleavage of focal adhesion kinase (pp125FAK), an important component of the focal adhesion complex, and identify pp125FAK as a novel substrate for caspase-3 and caspase-3-like apoptotic caspases. The initial cleavage precedes detachment, and coincides with loss of pp125FAK and paxillin from focal adhesion sites and their redistribution into the characteristic membrane blebs of apoptotically dying cells. Cleavage of pp125FAK differentially affects its association with signaling and cytoskeletal components of the focal adhesion complex; binding of paxillin, but not pp130(Cas) (Cas, Crk-associated substrate) and vinculin, to the COOH terminally truncated pp125FAK is abolished. Therefore, caspase-mediated cleavage of pp125FAK may be participating in the disassembly of the focal adhesion complex and actively interrupting survival signals from the extracellular matrix, thus propagating the cell death program.
Levkau
B
B
Department of Pathology, University of Washington School of Medicine, Seattle, Washington 98195-7470, USA.
Herren
B
B
Koyama
H
H
Ross
R
R
Raines
E W
EW
D017209:Apoptosis; D029742:Caenorhabditis elegans Proteins; D020170:Caspase 1; D020169:Caspases; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002478:Cells, Cultured; D050719:Crk-Associated Substrate Protein; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004730:Endothelium, Vascular / Q000502:physiology*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006133:Growth Substances / Q000502:physiology; D015801:Helminth Proteins / Q000378:metabolism; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins; D011972:Receptor, Insulin / Q000378:metabolism*; D050717:Retinoblastoma-Like Protein p130; D016596:Vinculin / Q000378:metabolism
C493841:BCAR1 protein, human; D029742:Caenorhabditis elegans Proteins; D015815:Cell Adhesion Molecules; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D006133:Growth Substances; D015801:Helminth Proteins; D007375:Interleukin-1; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D016596:Vinculin; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D020169:Caspases; D003546:Cysteine Endopeptidases; C089223:ced-3 protein, C elegans; D020170:Caspase 1